Material removal process for self-aligned contacts

Abstract

A method is disclosed of removing a first material disposed over a second material adjacent to a field effect transistor gate having a gate sidewall layer that comprises an etch-resistant material on a gate sidewall. The method includes subjecting the first material to a gas cluster ion beam etch process to remove first material adjacent to the gate, and detecting exposure of the second material during the gas cluster ion beam (GCIB) etch process.

What is claimed is: 
     
       1. A gas cluster ion beam etching apparatus, comprising:
 a gas expander to form gas clusters; 
 an ionizer and an accelerator to form a gas cluster ion beam; 
 a detector to detect exposure of a material at a target site during a gas cluster ion beam etch process; and 
 a controller to determine an amount of time required for the gas cluster ion beam etch process to expose the material based on detecting exposure of the material, 
 wherein the detector includes a probe movable between a position proximate to the target site and a position remote from the target site, and the controller directs the probe to the proximate position during etching of the target site and directs the probe to the remote position during etching of one or more additional target sites. 
 
     
     
       2. The apparatus of  claim 1 , wherein the controller terminates the gas cluster ion beam etch process in response to detecting exposure of the material. 
     
     
       3. The apparatus of  claim 1 , further comprising a spectrometer. 
     
     
       4. The apparatus of  claim 1 , further comprising a quadrupole mass spectrometer residual gas analyzer. 
     
     
       5. The apparatus of  claim 1 , further comprising a microplasma emission spectrometer. 
     
     
       6. The apparatus of  claim 1 , further comprising an optical probe for sensing an optical property of the material at the target site. 
     
     
       7. The apparatus of  claim 1 , further comprising a conduit for sampling gas and transporting it to the detector. 
     
     
       8. A gas cluster ion beam etching apparatus, comprising:
 a gas expander for forming gas clusters; 
 an ionizer and an accelerator for forming a gas cluster ion beam; 
 a detector for detecting material at a target site of the gas cluster ion beam; and 
 a controller to identify exposure of a second material under a first material at the target site in response to input from the detector, wherein the controller determines an etch duration needed to expose the second material at the target site on a semiconductor device wafer, and subjects one or more additional target sites on the wafer for said duration, and 
 wherein the detector includes a probe movable between a position proximate to the target site and a position remote from the target site, and the controller directs the probe to the proximate position during etching of the target site and directs the probe to the remote position during etching of said one or more additional target sites. 
 
     
     
       9. The apparatus of  claim 8 , wherein the controller terminates gas cluster ion beam etching in response to exposure of the second material. 
     
     
       10. The apparatus of  claim 8 , wherein the probe is an optical probe for sensing an optical property of the etch target. 
     
     
       11. The apparatus of  claim 8 , wherein the probe is a conduit for sampling gas and transporting it to the detector.